/*
 * @Description: 
 * @Version: 1.0
 * @Author: Vicro
 * @Date: 2020-11-28 21:36:58
 * @LastEditTime: 2020-11-28 21:41:55
 * @FilePath: \Leetcode\236.二叉树的最近公共祖先.cpp
 */
/*
 * @lc app=leetcode.cn id=236 lang=cpp
 *
 * [236] 二叉树的最近公共祖先
 */

// @lc code=start
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
        if (root == nullptr) return nullptr;
        if (root == p || root == q) return root;
        
        TreeNode* left = lowestCommonAncestor(root->left, p, q);
        TreeNode* right = lowestCommonAncestor(root->right, p, q);

        if (left == nullptr) return right;
        if (right == nullptr) return left;

        return root;
    }
};
// @lc code=end

